Electronic devices

ABSTRACT

An electronic device, such as a thin film transistor containing a semiconductor of the Formula: wherein R, R′ and R″ are, for example, independently hydrogen, a suitable hydrocarbon, a suitable hetero-containing group, a halogen, or mixtures thereof; and n represents the number of repeating units.

This application is a continuation from U.S. patent application Ser. No.11/586,449, filed Oct. 25, 2006. That application is hereby fullyincorporated by reference in its entirety.

CROSS REFERENCE TO RELATED APPLICATIONS

U.S. application Ser. No. 11/586,448, filed Oct. 26, 2010, onPoly(dithienylbenzo[1,2-b:4,5-b′]dithiophene) Polymers, by Beng S. Onget al.

U.S. application Ser. No. 11/398,981, filed Apr. 6, 2006, onFunctionalized Heteroacenes and Electronic Devices Generated Therefrom,by Yuning Li et al.

U.S. application Ser. No. 11/399,226, filed Apr. 6, 2006, onFunctionalized Heteroacenes, by Yuning Li et al.

U.S. application Ser. No. 11/399,216, filed Apr. 6, 2006, on Polyacenesand Electronic Devices Generated Therefrom, by Yuning Li et al.

U.S. application Ser. No. 11/399,064, filed Apr. 6, 2006, on HeteroacenePolymers and Electronic Devices Generated Therefrom, by Yuning Li et al.

U.S. application Ser. No. 11/399,169, filed Apr. 6, 2006, on EthynyleneAcene Polymers and Electronic Devices Generated Therefrom, by Yuning Liet al.

U.S. application Ser. No. 11/399,091, filed Apr. 6, 2006, on EthynyleneAcene Polymers, by Yuning Li et al.

U.S. application Ser. No. 11/399,231, filed Apr. 6, 2006, onPoly[bis(ethynyl)heteroacenes] and Electronic Devices GeneratedTherefrom, by Yuning Li et al.

U.S. application Ser. No. 11/399,141, filed Apr. 6, 2006, onSemiconductors and Electronic Devices Generated Therefrom, by Yiliang Wuet al.

U.S. application Ser. No. 11/399,230, filed Apr. 6, 2006, onSemiconductor Polymers, by Yiliang Wu et al.

U.S. application Ser. No. 11/398,941, filed Apr. 6, 2006, onPolydiazaacenes and Electronic Devices Generated Therefrom, by YiliangWu et al.

U.S. application Ser. No. 11/398,902, filed Apr. 6, 2006, onPolydiazaacenes, by Yiliang Wu et al.

U.S. application Ser. No. 11/398,931, filed Apr. 6, 2006, onPoly(alkynylthiophene)s and Electronic Devices Generated Therefrom, byBeng S. Ong et al.

U.S. application Ser. No. 11/399,246, filed Apr. 6, 2006, onPoly(alkynylthiophene)s, by Beng S. Ong et al.

U.S. application Ser. No. 11/399,092, filed Apr. 6, 2006, on LinkedArylamine Polymers and Electronic Devices Generated Therefrom, by YuningLi et al.

U.S. application Ser. No. 11/399,065, filed Apr. 6, 2006, on LinkedArylamine Polymers, by Yuning Li et al.

Illustrated in U.S. application Ser. No. 11/011,678, Publication No.20060124921 filed Dec. 14, 2004, relating to indolocarbazole moietiesand thin film transistor devices thereof.

Illustrated in U.S. application Ser. No. 11/167,512, Publication No.20060214155 filed Jun. 27, 2005, relating to indolocarbazole moietiesand thin film transistor devices thereof.

Illustrated in U.S. Pat. No. 6,770,904, and copending application U.S.application Ser. No. 10/922,662, Publication No. 20050017311, areelectronic devices, such as thin film transistors containingsemiconductor layers of, for example, polythiophenes.

The disclosure of each of the above cross referenced copendingapplications and patent are totally incorporated herein by reference. Inaspects of the present disclosure, there may be selected the appropriatesubstituents, such as a suitable hydrocarbon, a heteroatom containinggroup, hydrogen, halogen, CN, NO₂, rings, source and gate electrodes,substrates, number of repeating polymer units, number of groups, and thelike as illustrated in the copending applications.

BACKGROUND

The present disclosure is generally directed to semiconductors of theformulas as illustrated herein and processes of preparation and usesthereof. More specifically, the present disclosure in embodiments isdirected to novel polymers of the formulas as illustrated herein, andmore specifically, to poly(dithienylbenzo[1,2-b:4,5-b′]dithiophene)sselected as semiconductors for polymer thin-film transistors and alsowhich can be selected as solution processable and substantially stablechannel semiconductors in organic electronic devices, such as thin filmtransistors and which transistors are stable in air, that is do notsubstantially degrade over a period of time when exposed to oxygen.Although not desiring to be limited by theory, it is believed that thepresence of two thienylene functions in the semiconductor polymerassists in enhancing transistor performance, such as field effectmobility, for example there can be achieved TFT field effect mobility of10⁻² cm⁻²/v·s.

There are desired electronic devices and polymers thereof, such as thinfilm transistors, TFTs, fabricated with a semiconductor of the formulasas illustrated herein, and which semiconductors possess excellentsolvent solubility, and which can be solution processable; and whichdevices possess mechanical durability and structural flexibility,characteristics which are desirable for fabricating flexible TFTs on anumber of substrates, such as plastic substrates. Flexible TFTs enablethe design of electronic devices with structural flexibility andmechanical durability characteristics. The use of plastic substratestogether with the semiconductor of the formulas as illustrated hereincan transform the traditionally rigid silicon TFT into a mechanicallymore durable and structurally flexible TFT design. This can be ofparticular value to large area devices such as large-area image sensors,electronic paper and other display media. Also, the selection of p-typesemiconductors of the formulas as illustrated herein possess inembodiments extended conjugation for integrated circuit logic elementsfor low end microelectronics, such as smart cards, radio frequencyidentification (RFID) tags, and memory/storage devices, and enhancetheir mechanical durability, and thus their useful life span.

A number of semiconductor polymers are not, it is believed, stable whenexposed to air as they become oxidatively doped by ambient oxygenresulting in increased conductivity. The result is large off-current andthus low current on/off ratio for the devices fabricated from thesematerials. Accordingly, with many of these polymers, rigorousprecautions are usually undertaken during processing and devicefabrication to exclude environmental oxygen to avoid or minimizeoxidative doping. These precautionary measures increase the cost ofmanufacturing therefore offsetting the appeal of certain semiconductorTFTs as an economical alternative to amorphous silicon technology,particularly for large area devices. These and other disadvantages areavoided or minimized in embodiments of the present disclosure.

REFERENCES

Regioregular polyhexylthiophenes usually undergo rapid photo oxidativedegradation under ambient conditions, while the know polytriarylaminespossess some stability when exposed to air, however, these amines arebelieved to possess low field effect mobilities, disadvantages avoidedor minimized with the polymers of the formulas as illustrated herein.

Also, acenes, such as pentacenes, heteroacenes, and their derivativesare known to possess acceptable high field effect mobility when used aschannel semiconductors in TFTs. However, these materials can be rapidlyoxidized by, for example, atmospheric oxygen under light, and suchcompounds are not considered as processable at ambient conditions.Furthermore, when selected for TFTs, non-substituted acenes aresubstantially insoluble, thus they are essentially nonsolutionprocessable; accordingly, such compounds have been processed by vacuumdeposition methods that result in high production costs, eliminated orminimized with the TFTs generated with the semiconductors illustratedherein. Although some substituted acenes are soluble in organic solvent,they usually have poor thin film formation characteristics, and thus notsuitable for solution processing large area electronics.

A number of organic semiconductor materials has been described for usein field effect TFTs, which materials include organic small molecules,such as pentacene, see for example D. J. Gundlach et al., “Pentaceneorganic thin film transistors—molecular ordering and mobility”, IEEEElectron Device Lett., Vol. 18, p. 87 (1997); oligomers such assexithiophenes or their variants, see for example reference F. Gamier etal., “Molecular engineering of organic semiconductors: Design ofself-assembly properties in conjugated thiophene oligomers”, J. Amer.Chem. Soc., Vol. 115, p. 8716 (1993), and poly(3-alkylthiophene), seefor example reference Z. Bao et al., “Soluble and processableregioregular poly(3-hexylthiophene) for field-effect thin filmtransistor application with high mobility”, Appl. Phys. Lett. Vol. 69, p4108 (1996). Although organic material based TFTs generally providelower performance characteristics than their conventional siliconcounterparts, such as silicon crystal or polysilicon TFTs, they arenonetheless sufficiently useful for applications in areas where highmobility is not required. These include large area devices, such asimage sensors, active matrix liquid crystal displays, and low endmicroelectronics such as smart cards and RFID tags.

TFTs fabricated from p-type semiconductor polymers of the formulasillustrated herein may be functionally and structurally more desirablethan conventional silicons and other semiconductors in that they mayoffer mechanical durability, structural flexibility, and the potentialof being able to be incorporated directly onto the active media of thedevices, thus enhancing device compactness for transportability. Also, anumber of known small molecule or oligomer-based TFT devices rely ondifficult vacuum deposition techniques for fabrication. Vacuumdeposition is selected primarily because the materials selected areeither insoluble or their solution processing by spin coating, solutioncasting, or stamp printing do not generally provide uniform thin films.Vacuum deposition may also involve the difficulty of achievingconsistent thin film quality for large area format. Polymer TFTs, suchas those fabricated from regioregular components of, for example,regioregular poly(3-alkylthiophene-2,5-diyl) by solution processes,while offering some mobility, suffer from their propensity towardsoxidative doping in air. For practical low cost TFT design, it istherefore of value to have a semiconductor material that is both stableand solution processable, and where its performance is not adverselyaffected by ambient oxygen, for example, TFTs generated withpoly(3-alkylthiophene-2,5-diyl) are sensitive to air. The TFTsfabricated from these materials in ambient conditions generally exhibitlarge off-current, very low current on/off ratios, and their performancecharacteristics degrade rapidly.

BRIEF DESCRIPTION OF THE DRAWINGS

Illustrated in FIGS. 1 to 4 are various representative embodiments ofthe present disclosure, and wherein p-type semiconductors of theformulas as illustrated herein are selected as the channel orsemiconductor material in thin film transistor (TFT) configurations.

EMBODIMENTS

It is a feature of the present disclosure to provide semiconductors ofthe formulas/structures as illustrated herein which are useful formicroelectronic device applications, such as TFT devices.

It is another feature of the present disclosure to provide p-typesemiconductor polymers of the formulas/structures as illustrated hereinwith a band gap of from about 1.5 eV to about 3 eV as determined fromthe absorption spectra of thin films thereof.

In yet a further feature of the present disclosure there is providedp-type polymer semiconductors of the formulas/structures illustratedherein which are useful as microelectronic components, and whichpolymers possess a solubility of, for example, at least about 0.1percent to about 95 percent by weight in common organic solvents, suchas methylene chloride, tetrahydrofuran, toluene, xylene, mesitylene,chlorobenzene, dichlorobenzene, trichlorobenzene, and the like, and thusthese polymers can be economically fabricated by solution processes suchas spin coating, screen printing, stamp printing, dip coating, solutioncasting, jet printing, and the like.

Another feature of the present disclosure resides in providingelectronic devices, such as TFTs, with p-type semiconductors of theformulas as illustrated herein, and more specifically, apoly(dithienylbenzo[1,2-b:4,5-b′]dithiophene)s as semiconductors forpolymer containing thin film transistors, and which semiconductor layerhas a conductivity of, for example, from about 10⁻⁴ to about 10⁻⁹ S/cm(Siemens/centimeter).

Also, in yet another feature of the present disclosure there areprovided novel p-type semiconductors of the formulas as illustratedherein, and devices thereof, and which devices exhibit enhancedresistance to the adverse effects of oxygen, that is, these devicesexhibit relatively high current on/off ratios, and their performancedoes not substantially degrade as rapidly as similar devices fabricatedwith regioregular poly(3-alkylthiophene)s, or with acenes.

Additionally, in a further feature of the present disclosure there isprovided a class of novel p-type semiconductors of the formulas asillustrated herein with unique structural features which are conduciveto molecular self-alignment under appropriate processing conditions, andwhich structural features also enhance the stability of deviceperformance. Proper molecular alignment can permit higher molecularstructural order in thin film, which can be of value to efficient chargecarrier transport, and thus higher electrical performance.

There are disclosed in embodiments a polymer, and more specifically,semiconductors of the formulas as illustrated herein, and electronicdevices thereof. More specifically, the present disclosure relates tosemiconductor polymers illustrated by or encompassed byFormulas/Structures (I)

wherein R, R′, and R″ are independently at least one of hydrogen, asuitable hydrocarbon, a suitable hetero-containing group, and a halogenand where, for example, the hydrocarbon can be alkyl, alkoxy, aryl,substituted derivatives thereof, and the like, inclusive of side-chainscontaining, for example, from zero to about 30 carbon atoms, and morespecifically, from 1 to about 18 carbon atoms; and n represents thenumber of repeating units such as a number of from about 2 to about2,500, and more specifically, from about 2 to about 1,000, from about100 to about 800, or from about 2 to about 50. In embodiments, R is along carbon side-chain containing from about 6 to about 30 carbon atoms,and R′ or R″ is a substituent containing from 0 to about 5 carbon atoms;or R is a substituent containing from 0 to about 5 carbon atoms, and R′is a long carbon side-chain containing from 6 to about 30 carbon atoms.R, R′, and R″ are in embodiments, for example, independently hydrogen, asuitable hydrocarbon like alkyl, aryl, alkoxy, arylalkyl, alkylsubstituted aryls, and the like; and mixtures thereof; and n representsthe number of units, such as for example, n is a number of from about 2to about 5,000, and more specifically, from about 2 to about 1,000, orfrom about 2 to about 700. In embodiments, R, R′, and R″ are, morespecifically, alkyl, arylalkyl, and alkyl substituted aryls. Yet morespecifically, R, R′, and R″ are alkyl with about 1 to about 35 carbonatoms of, for example, methyl, ethyl, propyl, butyl, pentyl, hexyl,heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl,pentadecyl, hexadecyl, heptadecyl or octadecyl; arylalkyl with about 7to about 42 carbon atoms of, for example, methylphenyl(tolyl),ethylphenyl, propylphenyl, butylphenyl, pentylphenyl, hexylphenyl,heptylphenyl, octylphenyl, nonylphenyl, decylphenyl, undecylphenyl,dodecylphenyl, tridecylphenyl, tetradecylphenyl, pentadecylphenyl,hexadecylphenyl, heptadecylphenyl, and octadecylphenyl.

The number average molecular weight (M_(n)) of the polymers inembodiments can be, for example, from about 500 to about 400,000,including from about 1,000 to about 150,000, and the weight averagemolecular weight (M_(w)) thereof can be from about 600 to about 500,000,including from about 1,500 to about 200,000, both as measured by gelpermeation chromatography using polystyrene standards.

In embodiments, specific p-type channel semiconductors are representedby structures (1) through (20).

wherein each R′″ and R″″ independently represents at least one ofalkoxy, alkyl or substituted alkyl groups with, for example, from about1 to about 35 carbon atoms of, for example, an alkyl or substitutedalkyl of methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl,nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl,hexadecyl, heptadecyl, octadecyl, nonadecyl, eicosanyl, hydroxymethyl,hydroxyethyl, hydroxypropyl, hydroxybutyl, hydroxypentyl, hydroxyhexyl,hydroxyheptyl, hydroxyoctyl, hydroxynonyl, hydroxydecyl, hydroxyundecyl,hydroxydodecyl, methoxyethyl, methoxypropyl, methoxybutyl,methoxypentyl, methoxyoctyl, trifluoromethyl, perfluoroethyl,perfluoropropyl, perfluorobutyl, perfluoropentyl, perfluorohexyl,perfluoroheptyl, perfluorooctyl, perfluorononyl, perfluorodecyl,perfluoroundecyl, or perfluorododecyl; X represents F, Cl, Br, CN, orNO₂; n represents the number of repeating units of the polymer, and canbe, for example, from 2 to about 5,000, from about 5 to about 2,500,from about 5 to about 1,000, from about 5 to about 800, or from about 5to about 200; the number average molecular weight (M_(n)) of thepolymers can be, for example, from about 500 to about 400,000, includingfrom about 1,000 to about 150,000, and the weight average molecularweight (M_(w)) thereof can be from about 600 to about 500,000, includingfrom about 1,500 to about 200,000, both as measured by gel permeationchromatography using polystyrene standards.

In embodiments, examples of p-type channel semiconductors arerepresented by the following structures (21) through (33).

wherein n represents the number of repeating units of the polymer, andcan be, for example, from 2 to about 5,000, from about 5 to about 2,500,and more specifically, from about 5 to about 1,000, from about 5 toabout 800, or from about 5 to about 200. The number average molecularweight (M_(n)) of the polymers can be, for example, from about 500 toabout 400,000, including from about 1,000 to about 150,000, and theweight average molecular weight (M_(w)) thereof can be from about 600 toabout 500,000, including from about 1,500 to about 200,000, both asmeasured by gel permeation chromatography using polystyrene standards;or, more specifically, the p-type channel semiconductors are representedby the following structures

wherein n represents the number of repeating units of the polymer, andcan be, for example, from 2 to about 5,000, from about 5 to about 2,500,and more specifically, from about 5 to about 1,000, from about 5 toabout 800, or from about 5 to about 200. The number average molecularweight (M_(n)) of the polymers can be, for example, from about 500 toabout 400,000, including from about 1,000 to about 150,000, and theweight average molecular weight (M_(w)) thereof can be from about 600 toabout 500,000, including from about 1,500 to about 200,000, both asmeasured by gel permeation chromatography using polystyrene standards.

In embodiments, there are disclosed processes for the preparation of thepolymer type semiconductors of the formulas as illustrated herein inaccordance, for example, with the following Scheme 1. More specifically,the process for the preparation of the polymer semiconductor of Formula(22),poly(4,8-didodecyl-2,6-bis-(3-methyl-thiophen-2-yl)-benzo[1,2-b;4,5-b′]dithiophene),as illustrated herein, can be accomplished by, for example, i) reacting2,6-dibromo-4,8-didodecylbenzo[1,2-b;4,5;b′]dithiophene (preparedaccording to H. Pan, Y. Li, Y. Wu, P. Liu, B. S. Ong, S. Zhu, G. Xu,Chem. Mater., Vol. 18, p. 3237 (2006)) with 3-methylthiophene-2-boronicacid pinacol ester with a Suzuki coupling reaction in toluene in thepresence of 2M aqueous Na₂CO₃ (sodium carbonate) solution, and catalyticamount of Pd(PPh₃)₄ (tetrakis(triphenylphosphine palladium(0)) at 105°C. to generate the monomer,4,8-didodecyl-2,6-bis-(3-methyl-thiophen-2-yl)-benzo[1,2-b;4,5-b′]dithiophene;ii) polymerizing4,8-didodecyl-2,6-bis-(3-methyl-thiophen-2-yl)-benzo[1,2-b;4,5-b′]dithiophenein chlorobenzene with FeCl₃ (iron(III)chloride)-mediated oxidativecoupling reaction at about 65° C. for a suitable time, such as fromabout 35 to about 55, and more specifically 48 hours, to provide polymer(22) as a dark red solid. Polymer (23), where R═R′═R′=hexyl, wassimilarly synthesized.

The polymer semiconductors of Formulas/Structures (I) are soluble orsubstantially soluble in common coating solvents, for example, inembodiments they possess a solubility of at least about 0.1 percent byweight, and more specifically, from about 0.5 percent to about 10percent, or to about 95 percent by weight in such solvents as methylenechloride, 1,2-dichloroethane, tetrahydrofuran, toluene, xylene,mesitylene, chlorobenzene, dichlorobenzene, and the like. Moreover,p-type semiconductors of the formulas as illustrated herein provide astable conductivity of, for example, from about 10⁻⁹ S/cm to about 10⁻⁴S/cm, and more specifically, from about 10⁻⁸ S/cm to about 10⁻⁵ S/cm asdetermined by conventional four-probe conductivity measurements.

It is believed that the p-type semiconductors disclosed when fabricatedfrom solutions as thin films of, for example, from about 10 nanometersto about 500 nanometers, or from about 50 to about 300 nanometers inthickness are more stable in ambient conditions than similar devicesfabricated from poly(3-alkylthiophene-2,5-diyl). When unprotected, theaforementioned p-type semiconductors of the formulas as illustratedherein, and devices thereof are generally stable for a number of weeksrather than days or hours as is the situation withpoly(3-alkylthiophene-2,5-diyl) after exposure to ambient oxygen, thusthe devices fabricated from p-type semiconductors of the formulas asillustrated herein can provide higher current on/off ratios, and theirperformance characteristics do not substantially change as rapidly aspoly(3-alkylthiophene-2,5-diyl) when no rigorous procedural precautionshave been taken to exclude ambient oxygen during material preparation,device fabrication, and evaluation. P-type semiconductors, such as thepoly(dithienylbenzo[1,2-b:4,5-b′]dithiophene)s disclosed herein, are inembodiments stable, that is they do not substantially degrade whenexposed to oxygen.

In further aspects of the present disclosure, there is provided a thinfilm transistor comprised of a substrate, a gate electrode, a gatedielectric layer, a source electrode and a drain electrode, and incontact with the source/drain electrodes and the gate dielectric layer asemiconductor layer comprised of the polymers of Formula/Structure (I)such as a poly(dithienylbenzo[1,2-b:4,5-b′]dithiophene); an electronicdevice comprising a semiconductive component and wherein the device is athin film transistor, and the component is selected from the groupconsisting of at least one of apoly(dithienylbenzo[1,2-b:4,5-b′]dithiophene) of the followingFormulas/Structures (1) through (20).

wherein each R′″ and R″″ independently represents at least one of alkylor substituted alkyl groups with from about 1 to about 35 carbon atomsof, for example, an alkyl or substituted alkyl of methyl, ethyl, propyl,butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl,tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl,nonadecyl, eicosanyl, hydroxymethyl, hydroxyethyl, hydroxypropyl,hydroxybutyl, hydroxypentyl, hydroxyhexyl, hydroxyheptyl, hydroxyoctyl,hydroxynonyl, hydroxydecyl, hydroxyundecyl, hydroxydodecyl,methoxyethyl, methoxypropyl, methoxybutyl, methoxypentyl, methoxyoctyl,trifluoromethyl, perfluoroethyl, perfluoropropyl, perfluorobutyl,perfluoropentyl, perfluorohexyl, perfluoroheptyl, perfluorooctyl,perfluorononyl, perfluorodecyl, perfluoroundecyl, or perfluorododecyl; Xrepresents F, Cl, Br, CN, I or NO₂; n represents the number of repeatingunits of the polymer and can be, for example, from about 2 to about5,000, from about 5 to about 2,500, from about 5 to about 1,000, fromabout 5 to about 800, or from about 5 to about 200; the number averagemolecular weight (M_(n)) of the polymers can be, for example, from about500 to about 400,000, including from about 1,000 to about 150,000, andthe weight average molecular weight (M_(w)) thereof can be from about600 to about 500,000, including from about 1500 to about 200,000, bothas measured by gel permeation chromatography using polystyrenestandards; a TFT device wherein the substrate is a plastic sheet of apolyester, a polycarbonate, or a polyimide; the gate source and drainelectrodes are each independently comprised of gold, nickel, aluminum,platinum, indium titanium oxide, or a conductive polymer, and the gatedielectric is a dielectric layer comprised of silicon nitride or siliconoxide; a TFT device wherein the substrate is glass or a plastic sheet;the gate, source and drain electrodes are each comprised of gold, andthe gate dielectric layer is comprised of the organic polymerpoly(methacrylate), or poly(vinyl phenol); a device wherein thesemiconductor layer is formed by solution processes of spin coating,stamp printing, screen printing, or jet printing; a device wherein thegate, source and drain electrodes, the gate dielectric, andsemiconductor layers are formed by solution processes of spin coating,solution casting, stamp printing, screen printing, or jet printing; anda TFT device wherein the substrate is a plastic sheet of a polyester, apolycarbonate, or a polyimide; and the gate, source and drain electrodesare fabricated from the organic conductive polymer polystyrenesulfonate-doped poly(3,4-ethylene dioxythiophene), or from a conductiveink/paste compound of a colloidal dispersion of silver in a polymerbinder, and the gate dielectric layer is organic polymer or inorganicoxide particle-polymer composite; andpoly(dithienylbenzo[1,2-b:4,5-b′]dithiophene) polymers, and thin filmtransistors thereof.

DESCRIPTION OF THE FIGURES

In FIG. 1 there is schematically illustrated a TFT configuration 10comprised of a substrate 16, in contact therewith a metal contact 18(gate electrode), and a layer of an insulating dielectric layer 14 withthe gate electrode having a portion thereof or the entire gate incontact with the dielectric layer 14 on top of which layer 14 two metalcontacts, 20 and 22 (source and drain electrodes), are deposited. Overand situated between the metal contacts 20 and 22 is layer 12 comprisedof the poly(dithienylbenzo[1,2-b:4,5-b′]dithiophene) semiconductor,poly(4,8-didodecyl-2,6-bis-(3-methyl-thiophen-2-yl)-benzo[1,2-b;4,5-b′]dithiophene),of Formula (22) wherein n is 23, orpoly(4,8-dihexyl-2,6-bis-(3-hexyl-thiophen-2-yl)-benzo[1,2-b:4,5-b′]dithiophene),of Formula (23), where n is 24. The gate electrode can be included inthe substrate, in the dielectric layer, and the like throughout.

FIG. 2 schematically illustrates another TFT configuration 30 comprisedof a substrate 36, a gate electrode 38, a source electrode 40, and adrain electrode 42, an insulating dielectric layer 34, and thesemiconductor layer 32 ofpoly(4,8-didodecyl-2,6-bis-(3-methyl-thiophen-2-yl)-benzo[1,2-b;4,5-b′]dithiophene)of Formula (22), orpoly(4,8-dihexyl-2,6-bis-(3-hexyl-thiophen-2-yl)benzo[1,2-b:4,5-b]dithiophene)(23).

FIG. 3 schematically illustrates a further TFT configuration 50comprised of a heavily n-doped silicon wafer 56, which can act as a gateelectrode, a thermally grown silicon oxide dielectric layer 54, thepoly(dithienylbenzo[1,2-b:4,5-b′]dithiophene) semiconductor layer 52 ofpoly(4,8-didodecyl-2,6-bis-(3-methyl-thiophen-2-yl)-benzo[1,2-b;4,5-b′]dithiophene)(22), orpoly(4,8-dihexyl-2,6-bis-(3-hexyl-thiophen-2-yl)-benzo[1,2-b:4,5-b′]dithiophene)(23), and a source electrode 60, a drain electrode 62; and a gateelectrode contact 64.

FIG. 4 schematically illustrates a TFT configuration 70 comprised ofsubstrate 76, a gate electrode 78, a source electrode 80, a drainelectrode 82, p-type semiconductors of the formulas as illustratedherein semiconductor layer 72 ofpoly(4,8-didodecyl-2,6-bis-(3-methyl-thiophen-2-yl)-benzo[1,2-b;4,5-b′]dithiophene)of Formula (22), wherein n is 23, orpoly(4,8-dihexyl-2,6-bis-(3-hexyl-thiophen-2-yl)-benzo[1,2-b:4,5-b]dithiophene)(23), wherein n is 24, and an insulating dielectric layer 74.

Also, other devices not disclosed, especially TFT devices, areenvisioned, reference for example known TFT devices.

In some embodiments of the present disclosure, an optional protectinglayer may be incorporated on top of each of the transistorconfigurations of FIGS. 1, 2, 3 and 4. For the TFT configuration of FIG.4, the insulating dielectric layer 74 may also function as a protectinglayer.

In embodiments and with further reference to the present disclosure andthe Figures, the substrate layer may generally be a silicon materialinclusive of various appropriate forms of silicon, a glass plate, aplastic film or a sheet, and the like depending on the intendedapplications. For structurally flexible devices, a plastic substrate,such as for example polyester, polycarbonate, polyimide sheets, and thelike, may be selected. The thickness of the substrate may be, forexample, from about 10 micrometers to over 10 millimeters with aspecific thickness being from about 50 to about 100 micrometers,especially for a flexible plastic substrate, and from about 1 to about10 millimeters for a rigid substrate such as glass or silicon.

The insulating dielectric layer, which can separate the gate electrodefrom the source and drain electrodes, and in contact with thesemiconductor layer, can generally be an inorganic material film, anorganic polymer film, or an organic-inorganic composite film. Thethickness of the dielectric layer is, for example, from about 10nanometers to about 1 micrometer with a more specific thickness beingabout 100 nanometers to about 500 nanometers. Illustrative examples ofinorganic materials suitable as the dielectric layer include siliconoxide, silicon nitride, aluminum oxide, barium titanate, bariumzirconate titanate, and the like; illustrative examples of organicpolymers for the dielectric layer include polyesters, polycarbonates,poly(vinyl phenol), polyimides, polystyrene, poly(methacrylate)s,poly(acrylate)s, epoxy resin, and the like; and illustrative examples ofinorganic-organic composite materials include nanosized metal oxideparticles dispersed in polymers, such as polyester, polyimide, epoxyresin, and the like. The insulating dielectric layer is generally of athickness of from about 50 nanometers to about 500 nanometers dependingon the dielectric constant of the dielectric material used. Morespecifically, the dielectric material has a dielectric constant of, forexample, at least about 3, thus a suitable dielectric thickness of about300 nanometers can provide a desirable capacitance, for example, ofabout 10⁻⁹ to about 10⁻⁷ F/cm².

Situated, for example, between and in contact with the dielectric layerand the source/drain electrodes is the active semiconductor layercomprised of p-type semiconductors of the formulas as illustratedherein, and wherein the thickness of this layer is generally, forexample, about 10 nanometers to about 1 micrometer, or about 40 to about100 nanometers. This layer can generally be fabricated by solutionprocesses such as spin coating, casting, screen, stamp, or jet printingof a solution of p-type semiconductors of the present disclosure.

The gate electrode can be a thin metal film, a conducting polymer film,a conducting film generated from a conducting ink or paste, or thesubstrate itself (for example heavily doped silicon). Examples of gateelectrode materials include, but are not limited to aluminum, gold,chromium, indium tin oxide, conducting polymers, such as polystyrenesulfonate-doped poly(3,4-ethylenedioxythiophene) (PSS/PEDOT), aconducting ink/paste comprised of carbon black/graphite or colloidalsilver dispersion contained in a polymer binder, such as Electrodagavailable from Acheson Colloids Company, and silver filled electricallyconductive thermoplastic ink available from Noelle Industries, and thelike. The gate layer can be prepared by vacuum evaporation, sputteringof metals or conductive metal oxides, coating from conducting polymersolutions or conducting inks, or dispersions by spin coating, casting orprinting. The thickness of the gate electrode layer is, for example,from about 10 nanometers to about 10 micrometers, and a specificthickness is, for example, from about 10 to about 200 nanometers formetal films, and about 1 to about 10 micrometers for polymer conductors.

The source and drain electrode layer can be fabricated from materialswhich provide a low resistance ohmic contact to the semiconductor layer.Typical materials suitable for use as source and drain electrodesinclude those of the gate electrode materials such as gold, nickel,aluminum, platinum, conducting polymers, and conducting inks. Typicalthickness of this layer is, for example, from about 40 nanometers toabout 1 micrometer with the more specific thickness being about 100 toabout 400 nanometers. The TFT devices contain a semiconductor channelwith a width W and length L. The semiconductor channel width may be, forexample, from about 10 micrometers to about 5 millimeters with aspecific channel width being about 100 micrometers to about 1millimeter. The semiconductor channel length may be, for example, fromabout 1 micrometer to about 1 millimeter with a more specific channellength being from about 5 micrometers to about 100 micrometers.

The source electrode is grounded and a bias voltage of generally, forexample, about 0 volt to about −80 volts is applied to the drainelectrode to collect the charge carriers transported across thesemiconductor channel when a voltage of generally, for example, about+10 volts to about −80 volts is applied to the gate electrode.

Other known suitable materials not recited herein for the variouscomponents of the TFT devices of the present disclosure can also beselected in embodiments.

The following Examples are provided:

EXAMPLE I 1) Synthesis ofpoly(4,8-didodecyl-2,6-bis-(3-methyl-thiophen-2-yl)-benzo[1,2-b:4,5-b′]dithiophene)(22) (Scheme 1) a)4,8-Didodecyl-2,6-bis-(3-methyl-thiophen-2-yl)-benzo[1,2-b:4,5-b′]dithiophene

To a 100 milliliter 3-necked reaction flask, 1 gram of2,6-dibromo-4,8-didodeclybenzo[1,2-b:4,5;b′]dithiophene (preparedaccording to H. Pan, Y. Li, Y. Wu, P. Liu, B. S. Ong, S. Zhu, G. Xu,Chem. Mater., Vol. 18, p. 3237 (2006), the disclosure of which istotally incorporated herein by reference), 0.37 gram of3-methylthiophene-2-boronic acid pinacol ester, and 25 milliliters oftoluene were added. The resulting mixture was thoroughly stirred and waspurged with argon. Then 0.04 gram of tetrakis(triphenylphosphinepalladium(0)) (Pd(Ph₃P)₄), 0.3 gram of Aliquat in 5 milliliters toluene,and 3.5 milliliters of 2 M aqueous Na₂CO₃ were added to the mixture. Thereaction mixture obtained was stirred at 105° C. for 26 hours. Aftercooling to room temperature, about 23° C. to about 26° C., there wereadded 100 milliliters of toluene, and the organic layer was washed withdeionized water 3 times in a separatory funnel, dried over anhydrousMgSO₄, and filtered. After removing the solvent, the remaining solid waspurified by column chromatography on silica gel (eluent:hexane/dichloromethane, 7/1, v/v) and recrystallized from 2-propanol toyield yellow needle-like crystals. Yield: 0.57 gram (57 percent). ¹H NMR(CDCl₃, 300 MHz, ppm): δ 7.46 (s, 2H), 7.26 (d, J=5 Hz, 2H), 6.96 (d,J=5 Hz, 2H), 3.17 (t, 4H), 2.55 (s, 6H), 1.86 (m, 4H), 1.27 (br, 36H),0.90 (t, 6H).

¹³C NMR (CDCl₃, 300 MHz, ppm): δ 137.92, 136.77, 136.37, 135.49, 132.04,128.86 (2C), 124.72, 120.26, 33.74, 32.31, 30.33, 30.08, 30.04, 29.97(×2), 29.94, 29.91, 29.74, 23.08, 15.97, 14.55

b)Poly(4,8-didodecyl-2,6-bis-(3-methyl-thiophen-2-yl)-benzo[1,2-b:4,5-b′]dithiophene)(22)

A solution of the above prepared4,8-didodecyl-2,6-bis-(3-methyl-thiophen-2-yl)-benzo[1,2-b:4,5-b′]dithiophene(0.412 gram) in 10 milliliters of chlorobenzene was added drop-wisethrough a dropping funnel to a well-stirred mixture of FeCl₃(iron(III)chloride) (0.46 gram) in 10 milliliters of chlorobenzene in a50 milliliter round-bottom flask under an argon atmosphere over a periodof 1 minute. The resulting mixture was heated to 65° C. and maintainedat this temperature for 48 hours under a blanket of argon. After coolingdown to room temperature, 15 milliliters of chlorobenzene were added,and the solution was added to 200 milliliters of stirring methanol. Themixture was then ultrasonicated for 2 minutes before stirred at roomtemperature for 1 hour. The polymer was filtered out and added into awell stirred mixture of 200 milliliters of methanol, and 50 millilitersof ammonia aqueous solution (30 weight percent). The mixture wasultrasonicated for 30 minutes and then stirred at room temperature for 2hours. A dark red solid was obtained after filtration, which waspurified by Soxhlet extraction with methanol for 3 hours, hexane for 24hours, and heptane for 24 hours. Then chlorobenzene was used to extractpolymer for 24 hours. Removal of the solvent afforded 0.12 gram (46percent yield) ofpoly(4,8-didodecyl-2,6-bis-(3-methyl-thiophen-2-yl)-benzo[1,2-b;4,5-b′]dithiophene)(22) as a dark red solid. The molecular weight and distribution weremeasured by using high temperature GPC at 100° C., with M_(n)=16,550,M_(w)=65,300, and polydispersity: 3.95, against polystyrene standards.

2) Device Fabrication and Evaluation

There was selected a top-contact thin film transistor configuration asschematically illustrated, for example, in FIG. 3. The test device wascomprised of an n-doped silicon wafer with a thermally grown siliconoxide layer of a thickness of about 200 nanometers thereon. The waferfunctioned as the gate electrode while the silicon oxide layer acted asthe gate dielectric; the silicon oxide layer had a capacitance of about15 nF/cm² (nanofarads/square centimeter) as measured with a capacitormeter. The silicon wafer was first cleaned with isopropanol, argonplasma, isopropanol and air dried. Then the clean substrate was immersedin a 0.1 M solution of octyltrichlorosilane (OTS8) in toluene at 60° C.for 20 minutes. Subsequently, the wafer was washed with toluene,isopropanol and air-dried.Poly(4,8-didodecyl-2,6-bis-(3-methyl-thiophen-2-yl)-benzo[1,2-b;4,5-b′]dithiophene)(22) dissolved in dichlorobenzene at a concentration of 0.5 percent byweight was used to deposit the semiconductor layer. The solution wasfirst filtrated through a 1 micrometer syringe filter, and thenspin-coated onto the OTS8-treated silicon substrate at 1,000 rpm for 120seconds in a warm atmosphere resulting in thin film with a thickness ofabout 20 to about 50 nanometers. After being dried in vacuum oven at 70°C. for 5 to 10 hours, gold source and drain electrodes of about 50nanometers in thickness for each were deposited on top of thesemiconductor layer by vacuum deposition through a shadow mask withvarious channel lengths and widths, thus creating a series oftransistors of various dimensions.

The evaluation of field-effect transistor devices performance wasaccomplished in a black box (that is, a closed box which excludedambient light) at ambient conditions using a Keithley 4200 SCSsemiconductor characterization system. The carrier mobility, μ, wascalculated from the data in the saturated regime (gate voltage,V_(G)<source-drain voltage, V_(SD)) according to equation (1)I _(SD) =C _(i)μ(W/2L)(V _(G) −V _(T))²  (1)where I_(SD) is the drain current at the saturated regime, W and L are,respectively, the semiconductor channel width and length, C_(i) is thecapacitance per unit area of the gate dielectric layer, and V_(G) andV_(T) are, respectively, the gate voltage and threshold voltage. V_(T)of the device was determined from the relationship between the squareroot of I_(SD) at the saturated regime and V_(G) of the device byextrapolating the measured data to I_(SD)=0.

Another property of field-effect transistor is its current on/off ratio.This is the ratio of the saturation source-drain current at theaccumulation regime to the source-drain current at the depletion regime.

The transfer and output characteristics of the devices revealed thatpoly(4,8-didodecyl-2,6-bis-(3-methyl-thiophen-2-yl)-benzo[1,2-b:4,5-b′]dithiophene)(22) is a p-type semiconductor. Using transistors with a dimension ofW=5,000 μm and L=about 40 to about 90 μm, the following averageproperties from at least five transistors were obtained:

Mobility: about 0.08 to about 0.12 cm²/V·s

Current on/off: about 2 to about 6×10⁶

EXAMPLE II 1) Synthesis ofpoly(4,8-dihexyl-2,6-bis-(3-hexyl-thiophen-2-yl)-benzo[1,2-b:4,5-b′]dithiophene)(23) (Scheme 1) (a) Benzo[1,2-b:4,5-b′]dithiophene-4,8-dione wasprepared according to Beimling, P.; Koβmehl, G. Chem. Ber. Vol. 119, p.3198 (1986), the disclosure of which is totally incorporated herein byreference) (b) 4,8-Dihexynylbenzo[1,2-b:4,5-b′]dithiophene

To a solution of hexyne (6.71 grams, 81.7 mmol) in THF (20 milliliters)in a 100 milliliter flask equipped with a condenser under an argonatmosphere were added dropwise 36 milliliters (72 mmol) of 2 M solutionof isopropylmagnesium chloride in THF at room temperature. An exothermicreaction occurred upon addition. After addition, the reaction mixturewas heated at 50° C. for 95 minutes and cooled down to room temperature.Benzo[1,2-b:4,5-b′]dithiophene-4,8-dione (3 grams, 13.6 mmol) was added,and the mixture was heated at 50° C. for 1 hour before cooling down toroom temperature. Subsequently, a solution of 20 grams of SnCl₂ in 50milliliters 10 percent aq. HCl solution was added in a dropwise fashionfollowed by a further heating at 60° C. for 1 hour. After the reaction,the solvent was removed by vacuum evaporation, and the residue waspurified by passing through a silica-gel flash column (eluent:hexane/dichloromethane, 2/1, v/v). Recrystallization of the crudeproduct collected from flash chromatography from 2-propanol gave 3 grams(63 percent yield) of a red crystal after drying in vacuo.

¹H NMR (CDCl₃, 300 MHz, ppm): δ 7.59 (d, J=5.5 Hz, 2H), 7.51 (d, J=5.5Hz, 2H), 2.66 (t, 4H), 1.74 (m, 4H), 1.64 (m, 4H), 1.03 (t, 6H).

¹³C NMR (CDCl₃, 300 MHz, ppm): δ 140.60, 138.63, 127.97, 123.64, 112.59,100.75, 31.26, 22.43, 20.04, 14.08

(c) 4,8-Dihexylbenzo[1,2-b:4,5-b′]dithiophene

To a solution of the above prepared4,8-dihexynylbenzo[1,2-b:4,5-b′]dithiophene (3 grams, 8.6 mmol) in THF(150 milliliters) in a round-bottomed flask was added 10 percent Pd/C(0.90 gram, 0.86 mmol). The mixture was stirred under a hydrogenatmosphere at room temperature for 24 hours. The solvent was removed byvacuum evaporation, and the residue with the catalyst impurity waspurified by column chromatography on silica gel (eluent:hexane/dichloromethane, 2/1, v/v). Recrystallization of the productisolated from column chromatography from 20 milliliters of isopropanolin fridge afforded 1.54 grams (51 percent yield) of needle crystal afterdrying in vacuo.

(Caution: Hydrogen gas reacts with Pd/C violently, and may cause fire inthe presence of oxygen)

¹H NMR (CDCl₃, 300 MHz, ppm): δ 7.49 (d, J=5.8 Hz, 2H), 7.47 (d, J=5.8Hz, 2H), 3.20 (t, 4H), 1.82 (m, 4H), 1.48 (m, 8H), 1.35 (bs, 36H), 0.91(t, 6H).

¹³C NMR (CDCl₃, 300 MHz, ppm): δ 137.73, 136.26, 129.39, 126.23, 122.25,33.92, 30.11, 30.06, 30.03, 23.02, 14.51.

(d) 2,6-Dibromo-4,8-dihexylbenzo[1,2-b:4,5-b′]dithiophene

To a well-stirred solution of the above prepared4,8-dihexylbenzo[1,2-b:4,5-b′]dithiophene 3 (1.54 grams, 4.29 mmol) inCH₂Cl₂ (30 milliliters) and acetic acid (7.5 milliliters) in a 200milliliter 3-necked flask under an argon atmosphere was added powderedNBS (1.529 grams, 8.58 mmol) in small portions over a period of about 6minutes in the absence of light. The resulting reaction mixture wasstirred for 24 hours. After the reaction, the white precipitate formedwas isolated by filtration, washed with water and methanol, andrecrystallized from 40 milliliters acetone to provide 1.34 grams (60percent yield) of green needle crystal after drying in vacuo.

¹H NMR (CDCl₃, 300 MHz, ppm): δ 7.43 (s, 2H), 3.00 (t, 4H), 1.75 (m,4H), 1.44 (m, 4H), 1.35 (bs, 8H), 0.92 (t, 6H).

¹³C NMR (CDCl₃, 300 MHz, ppm): δ 139.04, 135.87, 127.99, 125.09, 115.29,33.76, 32.04, 29.95, 29.87, 22.96, 14.46

e) 3-Hexylthiophene-2-boronic acid pinacol ester

A 100 milliliter three-necked round-bottomed flask was charged withmagnetic stirrer, adding funnel and water condenser, and flushed withArgon and vacuumed three times at heating. Milligram turnings (0.83gram, 34.0 mmol) were added into the flask and the system was flushedwith Argon for 10 minutes before 10 milliliters of anhydrous ether wereadded. 2-bromo-3-hexyl-thiophene (7 grams, 28.3 mmol) with 20milliliters anhydrous ether was added into the adding funnel. Around 5milliliters of a thiophene solution were dropped slowly into the flaskand heated the flask a little bit with heat gun. The reaction startedthree minutes late with continuous bubbling of ether, and the thiophenesolution was dropped into the flask and the reaction was stirred at roomtemperature for another 2 hours. The Grignard solution was transferredto another 100 milliliter two-necked flask, and then cooled the solutionto −78° C. A white precipitate formed when cooled and the solutionbecame viscous. 2-Isopropoxy-4,4,5,5-tetramethyl-1,3,2-dioxaborolane (7milliliters, 34 mmol) was added through syringe at −78° C. Theprecipitates were dissolved during the adding. Then the solution waswarmed to room temperature and stirred for a further 18 hours. 15Milliliters of water were added and the layers resulting were separated.The aqueous layer was extracted with CH₂Cl₂ (3×50 milliliters), and thecombined organic fractions were dried (MgSO₄) and evaporated to dryness.Column chromatography on silica gel (eluent: hexane/dichloromethane,4/1, v/v) enabled isolation of the 7 grams (yield 84 percent) of theabove pure product e) as colorless liquid after dried in vacuo.

¹H NMR (CDCl₃, 300 MHz, ppm): δ 7.50 (d, J=5.1 Hz, 1H), 7.03 (d, J=5.1Hz, 1H), 2.90 (t, 2H), 1.56 (m, 2H), 1.34 (bs, 18H), 0.91 (t, 3H).

¹³C NMR (CDCl₃, 300 MHz, ppm): δ 155.01, 131.68, 130.68, 83.84, 32.17,32.07, 30.45 (×2), 29.44 (×2), 25.20 (×4), 23.04, 14.49.

f)4,8-Dihexyl-2,6-bis-(3-hexyl-thiophen-2-yl)-benzo[1,2-b:4,5-b′]dithiophene

To a 100 milliliter 3-necked reaction flask, 1.34 grams (2.59 mmol) of2,6-dibromo-4,8-dihexylbenzo[1,2-b;4,5;b′]dithiophene, 1.9 grams (6.48mmol) of 3-hexylthiophene-2-boronic acid pinacol ester, and 50milliliters of toluene were added. The resulting mixture was thoroughlystirred and was purged with argon. Then 0.06 gram oftetrakis(triphenylphosphine palladium(0)) (Pd(Ph₃P)₄), 0.64 gram ofAliquat in 5 milliliters of toluene, and 7.5 milliliters of 2 M aqueousNa₂CO₃ were added to the mixture. The reaction mixture obtained wasstirred at 105° C. for 26 hours. After cooling to room temperature,about 23° C. to about 26° C., there were added 100 milliliters oftoluene, and the resulting organic layer was washed with deionized water3 times in a separatory funnel, dried over anhydrous MgSO₄, andfiltered. After removing the solvent, the remaining solid was purifiedby column chromatography on silica gel (eluent: hexane/dichloromethane,10/1.5, v/v) and recrystallized from 2-propanol to yield yellowneedle-like crystals of f). Yield: 1.23 grams (49 percent).

¹H NMR (CDCl₃, 300 MHz, ppm): δ 7.44 (s, 2H), 7.28 (d, J=5 Hz, 2H), 7.01(d, J=5 Hz, 2H), 3.17 (t, 4H), 2.91 (t, 4H), 1.86 (m, 4H), 1.73 (m, 4H),1.36 (br, 24H), 0.91 (t, 12H).

¹³C NMR (CDCl₃, 300 MHz, ppm): δ 141.15, 137.99, 136.70, 136.14, 131.55,130.59, 128.84, 125.06, 120.56, 33.80, 33.12, 32.09, 31.21, 30.07,29.98, 29.87, 29.70, 23.02(×2), 14.48, 14.45.

g)Poly(4,8-dihexyl-2,6-bis-(3-hexyl-thiophen-2-yl)-benzo[1,2-b:4,5-b′]dithiophene)(23)

A solution of the above prepared4,8-dihexyl-2,6-bis-(3-hexyl-thiophen-2-yl)-benzo[1,2-b:4,5-b′]dithiophene(0.50 gram) in 5 milliliters of chlorobenzene was added drop-wisethrough a dropping funnel to a well-stirred mixture of FeCl₃(iron(III)chloride) (0.59 gram) in 5 milliliters of chlorobenzene in a50 milliliter round-bottom flask under an argon atmosphere over a periodof 1 minute with droplet through the syringe. The green solution turnedblack immediately after added to the FeCl₃ solution. 10 Milliliters ofchlorobenzene were used to clean the glassware. The resulting mixturewas heated to 65° C. and maintained at this temperature for 48 hoursunder a blanket of argon. After cooling down to room temperature, 15milliliters of chlorobenzene were added, and the solution was pouredinto 200 milliliters of methanol. The mixture was ultrasonicated for 20minutes before stirred at room temperature for 1 hour. The polymer wasfiltered out and added into a well stirred mixture of 200 milliliters ofmethanol and 50 milliliters of ammonia aqueous solution (30 percent).The mixture was ultrasonicated for 5 minutes and then stirred at roomtemperature for 3 days. A dark red solid g) was obtained afterfiltration, which was purified by Soxhlet extraction with methanol for 4hours, and heptane for 24 hours. Then chlorobenzene was used to extractpolymer for 16 hours. Removal of solvent and drying in vacuo provided 60milligrams (12 percent yield) of brown powder. The molecular weight anddistribution were measured by using high temperature GPC at 100° C.,with M_(n)=16,300, M_(w)=62,100, and polydispersity 3.81 againstpolystyrene standards.

2) Device Fabrication and Evaluation

There was selected a top-contact thin film transistor configuration asschematically illustrated, for example, in FIG. 3. The test device wascomprised of an n-doped silicon wafer with a thermally grown siliconoxide layer of a thickness of about 200 nanometers thereon. The waferfunctioned as the gate electrode while the silicon oxide layer acted asthe gate dielectric; the silicon oxide layer had a capacitance of about15 nF/cm² (nanofarads/square centimeter) as measured with a capacitormeter. The silicon wafer was first cleaned with isopropanol, argonplasma, isopropanol and air dried. Then the clean substrate wereimmersed in a 0.1 M solution of octyltrichlorosilane (OTS8) in tolueneat 60° C. for 20 minutes. Subsequently, the wafer was washed withtoluene, isopropanol, and air dried.Poly(4,8-dihexyl-2,6-bis-(3-hexyl-thiophen-2-yl)-benzo[1,2-b:4,5-b′]dithiophene)(23) dissolved in dichlorobenzene at a concentration of 0.5 percent byweight was used to deposit the semiconductor layer. The solution wasfirst filtrated through a 1 micrometer syringe filter, and thenspin-coated onto the OTS8-treated silicon substrate at 1,000 rpm for 120seconds in warm atmosphere, resulting in thin film with a thickness ofabout 20 to about 50 nanometers. After being dried in vacuum oven at 70°C. for 5 to 10 hours, gold source and drain electrodes of about 50nanometers in thickness for each were deposited on top of thesemiconductor layer by vacuum deposition through a shadow mask withvarious channel lengths and widths, thus creating a series oftransistors of various dimensions.

The evaluation of field-effect thin film transistor performance wasaccomplished in a black box (that is, a closed box which excludedambient light) at ambient conditions using a Keithley 4200 SCSsemiconductor characterization system. The carrier mobility, μ, wascalculated from the data in the saturated regime (gate voltage,V_(G)<source-drain voltage, V_(SD)) according to equation (1)I _(SD) =C _(i)μ(W/2L)(V _(G) −V _(T))²  (1)where I_(SD) was the drain current at the saturated regime, W and Lwere, respectively, the semiconductor channel width and length, C_(i)was the capacitance per unit area of the gate dielectric layer, andV_(G) and V_(T) were, respectively, the gate voltage and thresholdvoltage. V_(T) of the device was determined from the relationshipbetween the square root of I_(SD) at the saturated regime and V_(G) ofthe device by extrapolating the measured data to I_(SD)=0.

Another property of field-effect transistor was its current on/offratio. This was the ratio of the saturation source-drain current at theaccumulation regime to the source-drain current at the depletion regime.

The transfer and output characteristics of the devices revealed thatpoly(4,8-dihexyl-2,6-bis-(3-hexyl-thiophen-2-yl)-benzo[1,2-b:4,5-b′]dithiophene)(23) was a p-type semiconductor. Using transistors with a dimension ofW=5,000 μm and L=about 40 to about 90 μm, the following averageproperties from at least five transistors were obtained

Mobility: about 0.14 to about 0.20 cm²/V·s

Current on/off: about 10⁴ to about 10⁶

Thus, thin film transistor ofpoly(dithienylbenzo[1,2-b:4,5-b′]dithiophene)s encompassed byFormulas/Structures (I) was excellent semiconductors for electronicdevices. As a channel semiconductor in thin film transistors, theydemonstrated high field effect mobility and high current on/off ratio.In addition, the device fabrication and characterization wereaccomplished in ambient conditions, evidencing their oxidative stabilityfor a number of weeks as compared to regioregularpoly(3-alkylthiophene)s devices which were stable for about less thanone week.

The claims, as originally presented and as they may be amended,encompass variations, alternatives, modifications, improvements,equivalents, and substantial equivalents of the embodiments andteachings disclosed herein, including those that are presentlyunforeseen or unappreciated, and that, for example, may arise fromapplicants/patentees and others. Unless specifically recited in a claim,steps or components of claims should not be implied or imported from thespecification or any other claims as to any particular order, number,position, size, shape, angle, color, or material.

What is claimed is:
 1. A semiconductor homopolymer, wherein thesemiconductor homopolymer is apoly(dithienylbenzo[1,2-b:4,5-b′]dithiophene) of Formula (14), (15),(16), or (17):

wherein each R′″ independently represents alkyl or substituted alkylhaving from about 1 to about 35 carbon atoms; X represents F, Cl, Br,CN, or NO₂; and n is from about 2 to about 5,000.
 2. An electronicdevice comprising the semiconductor homopolymer of claim
 1. 3. Asemiconductor homopolymer of Formula (31), (32), or (33):

wherein the semiconductor homopolymer has a number average molecularweight (M_(n)) of from about 500 to about 400,000 and a weight averagemolecular weight (M_(w)) of from about 600 to about 500,000.
 4. Anelectronic device comprising the semiconductor homopolymer of claim 3.5. A semiconductor homopolymer of Formula (5), (6), (7), (8), (18), or(20):

wherein each R′″ and R″″ independently represents alkyl or substitutedalkyl having from about 1 to about 35 carbon atoms; X represents F, Cl,Br, CN, or NO₂; and n is from about 2 to about 5,000.
 6. An electronicdevice comprising the semiconductor homopolymer of claim 5.